LONDON -- Italian fashion designers Domenico Dolce and Stefano Gabbana have joined the exclusive club of billionaires, according to Bloomberg News.

The company's latest Billionaires Index, which looks at data as of Wednesday, listed the co-founders of the Dolce & Gabbana label as billionaires for the first time.

Rising global demand for luxury goods has driven up the valuations of big fashion brands, boosting the net worth of their owners and top executives, Bloomberg said.

For example, the stock of Italy’s Prada more than doubled in 2012, Michael Kors Holdings in the U.S. saw its shares rise 87 percent, and Germany’s Hugo Boss posted a 45 percent stock gain.

Bloomberg cited an October luxury goods report from consulting firm Bain & Co. that estimated that global sales of apparel, accessories, cosmetics and fragrances would end up rising 10 percent in 2012 to $275 billion, the third straight year of growth of at least 10 percent.

Bloomberg valued privately-held Dolce & Gabbana at currently $5.3 billion and estimated the net worth of the 54-year-old Dolce, who owns a 41.8 percent stake in the company, at $2.2 billion. Gabbana, 50, who controls a 40 percent stake, is worth an estimated $2.1 billion, according to Bloomberg.

Another big name in the Italian fashion world joins them in the ranks of global billionaires. Sandro Veronesi, the 53-year-old owner of lingerie company Calzedonia Group, has an estimated net worth of $1.9 billion, Bloomberg said. Calzedonia operates such brands as Intimissimi.

Other well-known fashion industry executives on the Bloomberg Billionaires Index include LVMH head Bernard Arnault ($30.1 billion) and Spain's Zara boss Amancio Ortega ($57.4 billion), who ranks third on the list, ahead of U.S. investor Warren Buffett ($51.0 billion).

Mexican business tycoon Carlos Slim and Microsoft chairman Bill Gates are at the top of the billionaires index with $78.0 billion and $63.7 billion in net worth, respectively.